The third generation partnership project (3GPP) standards are continuously evolving. Early releases focused primarily on voice communications, while more recent releases have directed attention to data communication services such as high speed packet access (HSPA). The continued development of packet access services is driven by the desire of mobile users to be connected to Internet from anywhere at any time for leisure, business or other pursuits.
Continuous Packet Connectivity (CPC) was introduced in Release 7 to keep a device on the high speed channels, (i.e., in active state), as long as possible while no data transfer is ongoing by reducing the negative effects of remaining active during periods of low activity, (i.e., reducing power consumption and reducing the bandwidth requirements for radio layer signaling during that time). Among the features implemented along with CPC are discontinuous transmission (DTX) and discontinuous reception (DRX). DTX patterns and DRX patterns along with associated sets of rules allow a wireless transmit/receive unit (WTRU) to turn off its transmitter and receiver during periods of low activity to conserve power.
Uplink DTX is a mechanism that defines how the WTRU will discontinuously transmit the dedicated physical control channel (DPCCH). The uplink DTX is configured by a radio network controller (RNC). The uplink DPCCH burst pattern and the uplink DPCCH preamble and postamble together define the discontinuous uplink DPCCH operation. Uplink DTX is dependent on enhanced dedicated channel (E-DCH) and high speed dedicated physical control channel (HS-DPCCH) activity. Uplink DTX may be configured without configuring downlink DRX.
FIG. 1 shows a DPCCH burst pattern for the uplink. Two DTX patterns (UE_DTX_cycle_1 and UE_DTX_cycle_2) are defined for a WTRU for discontinuous uplink DPCCH operation. Either UE_DTX_cycle_1 or UE_DTX_cycle_2 is applied dependent on the duration of E-DCH inactivity. UE_DTX_cycle_2 is used when there is no E-DCH transmission for a predetermined number of subframes. Accordingly, the DPCCH transmission rate is autonomously adapted to data transmission activity. For example, during higher data transmission activity the uplink DPCCH may be configured to transmit more frequently, while during lower data transmission activity the DPCCH may be configured to transmit less often to produce a DTX gain. The DPCCH burst patterns for different WTRUs serviced by a Node B may be offset so that different WTRUs may have their DPCCH transmission phase in their respective DTX cycles at different times.
DPCCH is transmitted whenever E-DCH or HS-DPCCH is transmitted. When a WTRU is not transmitting data on an E-DCH or an HS-DPCCH, the WTRU does not transmit DPCCH except for a short burst of sub-frames once every UE_DTX_cycle_1 sub-frames, (subframes 107, 109, 111, . . . ). If the WTRU has not transmitted E-DCH during the last Inactivity_Threshold_for_UE_DTX_cycle_2 sub-frames, (last E-DCH frame 101), the WTRU does not transmit DPCCH except for a short burst of sub-frames once every UE_DTX_cycle_2 sub-frames, (subframes 113, . . . ).
A dual cell high speed downlink packet access (DC-HSDPA) mode has been introduced wherein two HSDPA carriers are used for downlink transmissions to increase the throughput per cell. In a DC-HSDPA mode, a cell is covered by up to two HSDPA carriers (possibly adjacent) in the same band. The frequency diversity between the carriers may provide a gain. DC-HSDPA provides both an increase in throughput and a reduction in latency. In poor radio conditions, where other techniques such as multiple-input multiple-out (MIMO) may not be practical, DC-HSDPA allows more UEs access to higher data rates. On the network side, DC-HSDPA allows efficient load balancing across carriers in addition to some capacity gain. A WTRU may be configured for DC-HSDPA operation in a CELL_DCH state.
While DTX and DRX operations are well defined for single carrier operations, there is currently no mechanism to handle DRX operations in a DC-HSDPA mode. In addition, in case that an HS-SCCH is transmitted only one of the carriers, there is currently no mechanism to indicate to the WTRU on which carrier the associated HS-PDSCH is transmitted on.